Heat exchanger



March 31, 1953 F. A. HIERSCH HEAT EXCHANGER 2 SHEETS-SHEET 1 Filed Feb. 19, 1947 EXHAUST OUT Patented Mar. 31, 1953 HEAT EXCHANGER, H

Frederick A. Hiersch, Detroit, Mich., assignor to Continental Aviation & Engineering Corpora tion, Detroit, Mich., a corporation of Virginia Application February 19, 1947, semi No. 729,653

3 Claims. (Cl. 257-'228) This invention relates to heat exchangers, especially to a heat exchanger for an elastic fluid power plant such as a gas turbine power plant.

Recent demands for higher speeds in aircraft have resulted in extensive development of gas turbines. The high rate of fuel consumption in gas turbines has stimulated designers to find improved methods of increasing the efficiency of gas turbine power plants. One expedient for increasing efficiency is the heat exchanger.

It is an object of this invention to provide a heat exchanger which accomplishes a high rate of heat exchange but takes up a minimum of space. This is accomplished in a heat exchanger in which one fluid flows through apassageway which is annular in cross section and the other fluid is in contact with the interior wall and exterior wall of the annular passageway. A superheater is incorporated in the heat exchanger.

In the drawings:

Fig. 1 is a longitudinal sectional view through a gas turbine power plant, showing the compressor and turbine schematically and showing in cross section that portion of an encircling heat exchanger which lies to one side of the axis of said power plant.

Fig. 2 is a view in section substantially on line 22 of Fig. 1 and showing a substantial segment of the annular heat exchanger. 7

Fig. 3 is a view showing'one means of spacing a pair of tubes.

Fig. 4 is an end elevation view of the embodi ment shown in Fig. 3. v

Fig. 5 is a view showing another embodiment of spacing means.

Fig. 6 is an end elevation of the embodiment shown in Fig. 5.

Fig. '7 shows still another embodiment of a spacing means.

Fig. 8 is an end elevation of the embodiment shown in Fig. 7, and

Fig. 9 is a cross sectional view of a pair of tubes or conduits illustrating a method of increasing the heat exchange capacity of tubes or conduits.

Referring now to the drawings in detail, a gas turbine power plant is shown as being pro vided with a rotary air compressor 2 and a coaxial gas turbine 4. Both rotatable elements 2 and 4 rotate about an axis A--A. The gas turbine power plant of this invention may conveniently take a form similar to the gas turbine shown in patent application Serial Number 672,124, filed May 24, 1946, now Patent No. 2,553,867, and assigned to the assignee of this invention.

The heat exchanger of this invention comprises a plurality of pairs of concentrically disposed tubes or conduits, each pair consisting of an outer conduit 6 and an inner conduit 8 of sufficiently smaller diameter to provide an annular passageway 10 between them. The said pairs of conduits are disposed within an annular casing structure l2 which encircles the compressor and turbine 'assembly,being symmetrical about the axis thereof. V

The outer conduits 6 extend through and have their respective ends rigidly secured to inner end plates l4 and I6, while the respective end portions of theinner conduits 8 extend through and are rigidly attached to outer end plates l8 and 26 disposed in longitudinally spaced relation to the plates 14 and I6 substantially as shown in Fig. 1. The end plates I6 and 20 are secured to and supported by the casing l2, while the plates I 4 and I8 are supported by the conduits. The said plates l4 and 18 are joined at their outer peripheries to provide an inner annular airchamher or header 22 at one end of. the conduit pairs, while the plates I6 and 20, in conjunction with a portion of the outer peripheral wall of the casing l2, provide an inner annular air chamber or header 28 at the other'end ofsaid conduits. These headers are in' communication with the annular passageways I!) provided by the several pairs of concentric conduits 6 and 8, as will be readily understood from Fig. 1. The inner periphery of the header-22 is open and disposed adjacent the compressor 2 for the reception of air therefrom.

Theplate I4 carries a cylindrical wall l2 extending at rightangles to the plane of the plate, which wall in conjunctionwith the inner peripheral wall 24 of thecasing structure l2 provides an annular chamber 26 surrounding the turbine 4 radially inwardly of the ring of conduits and adapted to receive exhaust gases from said turbine. .The plate l8 has attached to it a spaced end wall 30, the said wall and plate providing an annular exhaust chamber'or header 32 disposed longitudinally outward of the header 22 and communicating with one end of the bores oi the inner conduits 8; and the plate 20 in conjunction with the spaced end wall 34 of the casing structure 12 provides an annular chamber or header 36 disposed longitudinally outward of and'adjacent the header 28, and in communication with the other ends of said inner conduit bores. 7 v r V The exhaust gas receiving chamber 26 communicates with the space enclosed by the casing structure through a connection 38, and said chamber 26 also communicates with the header 36 by means of a passage 40 in which is disposed a superheater 42. The exhaust header 32 and the interior of the casing structure i2 discharge through a common outlet passage it. The superheater 42 comprises a multiplicity of radially disposed tubes 46 extending across the passage 40, such tubes being rigidly mounted in the spaced concentric rings 56 and 52 forming part of the casing structure (see Fig. 2). As will be readily understood, the superheater tubes conduct air from the air header 28 to the air outlet 48 at the inner periphery of the casing.

Where the distance between end plates l4 and I5 is great, or the annular space between the two conduits is small, it will be desirable to provide some means of spacing the inner and outer conduits. Figures 3 and i show a method which consists of a wire 54 which is helically wrapped around the inner conduit 8. If desired, the wire 54 may be beaded at regular intervals so that the beads provide the desired space. This arrangement would permit a freer fiow of gas through the annular space than the arrangement shown. Figs. 5 and 6 show a spacer 56 which resembles an Elizabethan collar. The spacer 56 runs the full length of the annular space and serves to aid in the transfer of heat. In Figs. 7 and 8 the spacing is accomplished by dimpling the outer conduit 6 as shown at 53.

In order to promote the more efiicient transfer of heat, the conduit may be provided with heat transfer aids such as are shown in Fig. 9. In this figure an Elizabethan collar type of highly conductive sheet metal strip 88 is shown crinkled somewhat in the shape of an Elizabethan collar and secured to the exterior of conduit 6. The annular space between conduits 6 and 8 is filled with a similarly crinkled strip 62. In this case the strip material 52 will serve as a spacer in much the same manner as the strip 56 of the Fig. 6 Similarly, the interior of inner conduit 8 is filled with a quantity of crinkled material 5 Operation Air under pressure is discharged from the fan 2 into the annular chamber or header 22, whence it passes into the annular space it between inner and outer conduits 8 and 5 respectively. The heated air discharges into a chamber or header 28, whence it passes through conduits 4% of superheater A2 and leaves the heat exchanger by way of outlet Exhaust gas is discharged from the turbine 4 into receiving chamber 25. From chamber 26 a portion of the exhaust gas passes through connection 38 into the space defined by the casing 12 and the exterior of outer conduits ii. The exhaust gas in this space fiows over the outside of conduits 6 giving up heat to the air in the annular passages. The remainder of the hot exhaust gas flows across conduits 45 or": super-heater d2 into chamber or header 3E, whence it passes through inner conduits 8 and gives up heat to the air in the annular passages It. The gas inside the inner conduits discharges into chamber or header 32 whence it passes to the exhaust outlet 44 where it mingles with the other exhaust gas.

With the arrangement shown, a maximum of efiiciency is obtained because of the fact that exhaust gas in the connection 59 is substantially at its highest temperature, and the air, just prior to its entry into the conduits 45, has reached as '4 high a temperature as possible in its passage through the annular space between the two conduits 6 and 8. In this way it is possible to bring the temperature of the air leaving the heat exchanger very close to the temperature of the exhaust gas leaving the turbine.

I claim:

1. A heat exchanger for a fluid turbine comprising spaced pairs of inner and outer headers, conduits connecting said spaced inner headers, second conduits extending longitudinally through the first mentioned conduits and concentrically spaced therewith to provide an annular passage connecting said inner headers, said second conduits connecting said outer headers, a casing structure surrounding and supporting said conduits and headers, said structure having an air outlet and an exhaust gas outlet, one of said inner headers having an air inlet and the other or said inner headers having an air outlet adjacent said air outlet of the casing structure, a superheater disposed between said adjacent air outlets of said casing and said last mentioned inner header, said casing having an exhaust gas receiving chamber having separate outlet passages, one of said outlet passages discharging the exhaust gases into the casing between the pair of inner headers in heat conductive relation with the first mentioned conduits, and the other outlet passage di charging the exhaust gases in heat exchange relation with respect to said superheater and thence into the adjacent outer headers, the conduits connecting said outer headers exhausing said exhaust gases from one outer header to the other and thence to said casing outlet means, said exhaust gas outlet of said casing structure comprising a common outlet for both streams of exhaust gases traversing the heat exchanger.

2. A heat exchanger for a fluid turbine comprising spaced pairs of inner and outer headers, conduits connecting said spaced inner headers, second conduits extending longitudinally through the first mentioned conduits and concentrically spaced therewith to provide an annular passage connecting said inner headers, said second conduits connecting said outer headers, a casing structure surrounding and supporting said conduits and headers, said structure having an air outlet, and an exhaust gas outlet, one of said inner headers having an air inlet and the other of said inner headers having an air outlet adjacent said air outlet of the casing structure, a superheater within the casing and disposed between said adjacent outlets of said casing and said last mentioned inner header, said casing having an exhaust gas receiving chamber having separate outlet passages, one of said outlet passages discharging the exhaust gases into the casing between the pair of inner headers in heat conductive relation with the first mentioned conduits, and the other outlet passage discharging the exhaust gases in heat exchange relation with respect to said superheater and thence into the adjacent outer header, the conduits connecting said outer headers exhausting said exhaust gases from one outer header to the other and thence to said casing outlet means, said exhaust gas outlet of said casing structure comprising a common outlet for both streams of exhaust gases traversing the heat exchanger, said headers comprising annular ringlike chambers, the air outlet means of the casing structure being disposed to exhaust the heated air from said heat exchanger substantially radially inwardly toward the central axis of said annular ringlike chambers.

3. A heat exchanger for a fluid turbine comprising spaced pairs of inner and outer headers, conduits connecting said spaced inner headers, second conduits extending longitudinally through the first mentioned conduits and concentrically spaced therewith to provide an annular passage connecting said inner headers, said second conduits connecting said outer headers, a casing structure surrounding and supporting said con duits and headers, said structure having an air outlet, and an exhaust gas outlet, one of said inner headers having an air inlet and the other of said inner headers having an air outlet adjacent said air outlet of the casing structure, a superheater within the casing and disposed between the air outlets of said casing and said last mentioned inner header, said casing having an exhaust gas receiving chamber having separate outlet passages, one of said outlet passages dis-1- oharging exhaust gases into the casing between the pair of inner headers in heat conductive relation with the first mentioned conduits, and the other outlet passage discharging exhaust gases in heat exchange relation with respect to said superheater and thence into the adjacent outer header, the conduits connecting said outer headers exhausting said exhaust gases from one outer header to the other and thence to said casing outlet means, said exhaust gas outlet of said casing structure comprising a common outlet for both streams of exhaust gases traversing the heat exchanger, said headers comprising an nular ring-like chambers, the air outlet means of the casing structure being disposed to exhaust the heated air from said heat exchanger substantially radially inwardly, said superheater comprising a plurality of conduits connected with one of said inner headers and extending substantially radially inwardly transverse of the lastmentioned outlet passage. 7

FREDERICK A. HIERSCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

